MIMO communication system

• US 20050107057A1
• Filed: 08/05/2004
• Published: 05/19/2005
• Est. Priority Date: 10/10/2003
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Sun, Yong
• Granted Patent: US 7,302,231 B2
• Time in Patent Office: Days
• US Class Current: 455/272
• CPC Class Codes: H04B 7/0845 per branch equalization, e.g. by an FIR-filter or RAKE receiver per antenna branch rake receivers as such H04B1/7115
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
• CPC Class Codes: H04B 7/0891 Space-time diversity rake receivers H04B1/7115; space-time decoding H04L1/0631
• CPC Class Codes: H04L 2025/03375 Passband transmission
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/0236 using estimation of the other symbols
• CPC Class Codes: H04L 25/03006 Arrangements for removing intersymbol interference

Abstract

The invention provides a generic and comprehensive architecture to optimise several space-time adaptive algorithms and their applications for both CCI and ISI interference cancellation for MIMO systems. The basic idea of this invention is to optimise space-only processes and time-only processes and their combination to take account of the varying affects of CCI and ISI in a given environment. This maximises the efficiency of adaptive algorithms. The invention is targeting on unknown CCI or co-antenna interference of other operating system at the same frequency band.

Claims

1. A method of obtaining an estimate of a transmission channel to a receiver, the method comprising:

a) receiving input signals from a plurality of receive antennas, said input signals being based upon a predetermined training sequence which has been transmitted to said receiver;

b) determining a first estimate of said transmission channel, based upon said input signals and said predetermined training sequence;

c) carrying out co-channel interference cancellation on said input signals using said first transmission channel estimate, to provide an intermediate signal;

d) determining a second estimate of said transmission channel based upon said intermediate signal and said predetermined training sequence;

e) carrying out inter-symbol interference cancellation on said intermediate signal using said second transmission channel estimate, to provide an output signal; and

f) carrying out the following steps one or more times;

i) revising said first transmission channel estimate based upon said input signals, said predetermined training sequence and said second channel estimate;

ii) carrying out co-channel interference cancellation on said input signals using said revised first transmission channel estimate, to provide a revised intermediate signal;

iii) revising said second transmission channel estimate based upon said revised intermediate signal, said predetermined training sequence and said second channel estimate; and

iv) carrying out inter-symbol interference cancellation on said revised intermediate signal using said revised second transmission channel estimate, to provide a revised output signal.

2. A method according to claim 1 wherein said step of carrying out co-channel interference comprises beamforming said input signal.

3. A method according to claim 2 wherein beamforming comprises applying adaptive weights to said input signal.

4. A method according to claim 3 wherein weights are determined based upon a comparison between said intermediate signal and a reference signal generated from said first estimate of said transmission channel and said predetermined training sequence.

5. A method according to claim 1 further comprising:

g) carrying out inter-system interference cancellation on said input signals prior to said co-channel interference cancellation, said inter-system interference cancellation being based upon said first estimate of said transmission channel.

6. A method according to claim 1 wherein said output data is processed to provide reference estimate data and wherein said reference estimate data is used in one or more of steps d), iii) and e).

7. A method according to claim 5 wherein said output data is processed to provide reference estimate data and wherein said reference estimate data is used in one or more of steps d), iii), e) and g).

8. A method according to claim 6 wherein said reference estimate data is obtained by deinterleaving and then decoding said output signal followed by reinterleaving.

9. A receiver adapted to operate according to the method of any one of the preceding claims.

10. A method according to claim 1 comprising after step f):

obtaining a final revised first transmission channel estimate and a final revised second transmission channel estimate,

carrying out a pre-filtering step in said transmitter and a corresponding post-filtering step on said intermediate data prior to carrying out inter-symbol interference, and

optimising said pre-filtering step and said post-filtering step based upon said final revised first transmission channel estimate and said final revised second transmission channel estimate.

11. Processor control code to, when running, implement the method of any one of claims 1 to 8.

12. A carrier carrying processor control code to, when running, implement the method of any one of claims 1 to 8.

13. A receiver for optimising an estimate of a transmission channel over which signals based upon a predetermined training sequence are being transmitted to said receiver, the receiver comprising:

a training sequence generator for generating a training sequence;

a plurality of antennas for producing input signals based upon said signals transmitted to said receiver;

first transmission channel estimator for generating a first transmission channel estimate based upon said input signals and said predetermined training sequence;

co-channel interference canceller for cancelling co-channel interference in said input signals and using said first transmission channel estimate, to provide an intermediate signal;

second transmission channel estimator for generating a second transmission channel estimate based upon said intermediate signal and said predetermined training sequence and further adapted for selectively generating a revised second transmission channel estimate based upon said intermediate signal, said predetermined training sequence and a previously calculated second transmission channel estimate; and

inter-symbol interference canceller for cancelling inter-symbol interference in said intermediate signal using said second transmission channel estimate, to provide an output signal, wherein

said second transmission channel estimator is adapted to feed back said second transmission channel estimate to said first transmission channel estimator; and

said first transmission channel estimator is adapted to selectively use said second transmission channel estimate along with said input signals and said predetermined training sequence for generating a revised first transmission channel estimate.

14. A receiver according to claim 13 wherein said co-channel interference canceller includes a beamformer for beamforming said input signals.

15. A receiver according to claim 14 wherein said beamformer comprises adaptive weighters for applying variable weights to paths through the beamformer.

16. A receiver according to claim 15 wherein said weights are controlled by a weight controller and said weight controller adjusts said weights based upon a comparison of the output from the beamformer and a reference output based upon the first transmission channel estimate and said predetermined training sequence.

17. A receiver according to claim 13 further comprising:

an inter-system interference canceller for carrying out inter-system interference cancellation on said input signals and outputting the inter-system interference cancelled input signals to said co-channel interference canceller, said inter-system interference cancellation being based upon said first transmission channel estimate.

18. A receiver according to claim 13 further comprising:

an output processor for deinterleaving and decoding said output signal to provide reference estimate data, and

an interleaver for reinterleaving said reference estimate data for use in at least one of said second transmission channel estimator and said inter-symbol interference canceller.

19. A receiver according to claim 17 further comprising:

an output processor for deinterleaving and decoding said output signal to provide reference estimate data, and

an interleaver for reinterleaving said reference estimate data for use in at least one of said second transmission channel estimator, said inter-symbol interference canceller and said inter-system interference canceller.